2/O T. H. MORGAN. 



are more apparent the longer the time that elapses before the 

 basal pieces are removed. The differences are not very marked 

 at the different levels indicating perhaps that changes take place 

 throughout the piece and not only at the basal end although 

 more pronounced in the latter. The different levels of the cuts 

 make it difficult to ascribe the results solely to the general 

 changes in the piece, for the more orally situated cut ends have 

 an advantage in level as other experiments have shown. 



Experiment III. - - Pieces were cut off at the same oral levels. 

 After 23 hours the hydranth region at the oral end was cut off 

 of some pieces (^4), others were cut in two in the middle of the piece 

 (.Z?), and for a control some pieces were left as before (C\ A 

 slight retardation occurred after another 12 hours in (A}, less 

 in (Z?) as compared with ((7). Removal of the hydranth forming 

 region after 23 hours causes delay but the delay is not so much 

 as though a new hydranth had developed at the new cut, show- 

 ing that changes directed towards hydranth formation are going 

 on not only in the region where the hydranth will develop but at 

 more basal levels as well. 



Experiment IV. - - This experiment was like the last, except 

 that the basal ends of all the pieces were tied, thus preventing the 

 basal end from exerting any influence on the result. Other ex- 

 periments had shown, however, that the basal development, even 

 if it occurs, has apparently no retarding influence on the oral de- 

 velopment. The results, as was to be expected, were the same 

 as in the last experiment. It is interesting to note that in both 

 the influence of the cutting causes a greater delay in the first ap- 

 pearance of the primordia of the hydranth than on their later 

 development ; for later the differences seem to be less than at 

 first. This may be due to an acceleration extending through- 

 out the whole time that is more effective after a beginning has 

 been made than before the start. 



Experiment V. Some previous experiments had left undecided 

 the question whether, when the oral end is left open for several 

 hours and is then tied off, the basal development is more rapid 

 than when the oral end is tied at once. If such an acceleration 

 really occurs it might seem to indicate that changes take place 

 in the oral end that produce accelerating materials even for the 



